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Topic: Basic Rocket Science Q & A (Read 380573 times)

The cube/square relationship of volume to surface area means that smaller LVs have higher aero losses. You get similar effects with the minimum gauge of materials.

That's true - smaller LV will have higher relative air drag. Can you, please, give some example of the effects that appear "with the minimum gauge of materials"? That's what interest me the most.

For example if you reduce the dimensions of a fuel tank by half and reduce the thickens of walls by half, tank will still have same mass fraction. I would guess this is example where scaling is possible. I don't have any experience in building rocket hardware so I could be wrong.

Danny, if you or anyone else would like, I could port that code to C, C++, or Java, since some people might find it easier to read or use that way. I was thinking of doing that anyway, since I'm one of those who, despite having started with QB, finds C-like languages more readable, but it occurred to me that others might find such a translation useful...

c might be useful to many out there. Lot is c code in the world today. By the way, you must be a really strange dude if you think c is inherently more readable than QB ;-)

Slightly off-topic:Once upon a time, I thought the same as you... then I actually switched to C, used it for a few years, and I came to see the beauty and simplicity in single-character braces as opposed to constantly capitalized potential polysyllabic keywords (woo, alliteration!), shorter type-names, and always declaring your variables before using them. Then again, I do find myself working with regular expressions from time to time, which are of a whole order less readable than BASIC or C...

This is not to say that beautiful BASIC code is impossible, or that ugly C-syntax code is impossible. Idiomatic C++ is particularly hard on the eyes at times, for sure.

I'll do that port tomorrow, then, when I have more caffeine in my system.

Thanks for reminding me about HTP. I might have to think about acquiring some for my garage project. The catalytic decomposition eases ignition, and it doesn't have any nitrogen in it to murder your Isp.

Be very, very careful!

HTP is catalyzed by a lot of organic sustances, including leather and human skin. Have plenty of water around to dilute any spills and a shower for any one exposed. Never work alone as the pain from exposure can prevent someone from treating themself.

IIRC, an amateur rocketry enthusiast died a couple of years ago working with HTP.

Do plenty of research.

Definitely planning on it. I have a few brains at KSC I will likely pick, regarding general safety practices with strong oxidizers. Might invest in something like a butyl coverall if I do go through with it. The "hypergolic with test engineers" issue is definitely not to be taken lightly.

Note also that to get high mass ratios you need BIG rocket ships. That follows because there are minimum weights to many rocket parts. This is known as 'minimum gauge', meaning that you can't make it any thinner or lighter. Combustion chambers have to be rugged. Pipes must be thick enough to hold pressures that don't get smaller just because you're trying to make a small sized rocket.

Danny, if you or anyone else would like, I could port that code to C, C++, or Java, since some people might find it easier to read or use that way. I was thinking of doing that anyway, since I'm one of those who, despite having started with QB, finds C-like languages more readable, but it occurred to me that others might find such a translation useful...

c might be useful to many out there. Lot is c code in the world today. By the way, you must be a really strange dude if you think c is inherently more readable than QB ;-)

And, if you don't object, I'll have a bash at putting it into Python.

Any particular wishes concerning a licence to be attached? Otherwise I'll tag it as being GPL which will keep your name attached and prevent somebody rolling it into their commercial product yet allow others to make improvements.

Rick

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I am not interested in your political point scoring, Ad Hominem attacks, personal obsessions and vendettas. - No matter how cute and clever you may think your comments are.

Danny, if you or anyone else would like, I could port that code to C, C++, or Java, since some people might find it easier to read or use that way. I was thinking of doing that anyway, since I'm one of those who, despite having started with QB, finds C-like languages more readable, but it occurred to me that others might find such a translation useful...

c might be useful to many out there. Lot is c code in the world today. By the way, you must be a really strange dude if you think c is inherently more readable than QB ;-)

And, if you don't object, I'll have a bash at putting it into Python.

Any particular wishes concerning a licence to be attached? Otherwise I'll tag it as being GPL which will keep your name attached and prevent somebody rolling it into their commercial product yet allow others to make improvements.

Rick

Thanks for asking. Sounds like a good idea. Is that what GNU does to their code?

c might be useful to many out there. Lot is c code in the world today. By the way, you must be a really strange dude if you think c is inherently more readable than QB ;-)

I never liked C, but then I never really used it beyond an intro course in college. Hate to say it, but I haven't really done any programming since my FORTRAN 77 days in school!

I saved my Fortran text for years, though what box it's in now... probably the same box as the Prolog, Pascal, and LISP books. I do most of my work with Visual Studio, these days, so that means C#, which is charitably described as "C-flavored."

c might be useful to many out there. Lot is c code in the world today. By the way, you must be a really strange dude if you think c is inherently more readable than QB ;-)

I never liked C, but then I never really used it beyond an intro course in college. Hate to say it, but I haven't really done any programming since my FORTRAN 77 days in school!

I saved my Fortran text for years, though what box it's in now... probably the same box as the Prolog, Pascal, and LISP books. I do most of my work with Visual Studio, these days, so that means C#, which is charitably described as "C-flavored."

Oh - now I 'C'. (grin)

You may find this a little strange, but I actually prefer VB. It's very conversational and sufficiently structured that I can do just about anything I want. Of course C is more powerful; it's just not as much fun. Plus most Macro applications for Window-based software is executed by VB. Makes it convenient to be conversant with it.

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Chuck - DIRECT co-founderI started my career on the Saturn-V F-1A engine

Any particular wishes concerning a licence to be attached? Otherwise I'll tag it as being GPL which will keep your name attached and prevent somebody rolling it into their commercial product yet allow others to make improvements.

Rick

Thanks for asking. Sounds like a good idea. Is that what GNU does to their code?

Danny Deger

Yes. There are a few variations on a theme. The LGPL (also GNU) is the main one - which allows inclusion into commercial products as a stand alone library.

There are lots of small variations, if you really want to get deep into things.

Two reasonably simple comparisons (assuming you want to be Open Source)

Are there any general guidelines for sizing diameter versus length for a cylindrical ELV with a given LEO payload capacity, specific impulse, and propellant density?

Suppose you wish to launch a payload with a relatively large diameter for its mass. Would it be better to launch it in a fat PLF on a skinnier LV or to launch it on a relatively short and squat LV that matches the PLF?

In other words, is there a "golden aspect ratio" for earth-launched rockets, and to what extent does the diameter of the payload affect the optimal diameter of the rocket?

Are there any general guidelines for sizing diameter versus length for a cylindrical ELV with a given LEO payload capacity, specific impulse, and propellant density?

Suppose you wish to launch a payload with a relatively large diameter for its mass. Would it be better to launch it in a fat PLF on a skinnier LV or to launch it on a relatively short and squat LV that matches the PLF?

- constant cylindrical LV diameter has two advantages1. PLF is lighter; it need not reach inwards to skinny rocket body2. less turbulent air flow

- payload dimensions vary; so adapt the LV to a certain mass and adapt the fairing to individual volume requirement

Quote

In other words, is there a "golden aspect ratio" for earth-launched rockets, and to what extent does the diameter of the payload affect the optimal diameter of the rocket?

Don't know about golden rules:Suggest to let the denser one of the two fuel/oxidizer 2nd (upper) stage components drive the diameter of its spherical tank. The other three tanks of upper and core stage will be more cylindrically elongated corresponding to their larger volumes. The 4 tank stack gives a rough estimate of length to diameter ratio for a given propellant.

Mind you, I do not build these things myself; others please correct or expand on solid propellants.

c might be useful to many out there. Lot is c code in the world today. By the way, you must be a really strange dude if you think c is inherently more readable than QB ;-)

I never liked C, but then I never really used it beyond an intro course in college. Hate to say it, but I haven't really done any programming since my FORTRAN 77 days in school!

I saved my Fortran text for years, though what box it's in now... probably the same box as the Prolog, Pascal, and LISP books. I do most of my work with Visual Studio, these days, so that means C#, which is charitably described as "C-flavored."

Oh - now I 'C'. (grin)

You may find this a little strange, but I actually prefer VB. It's very conversational and sufficiently structured that I can do just about anything I want. Of course C is more powerful; it's just not as much fun. Plus most Macro applications for Window-based software is executed by VB. Makes it convenient to be conversant with it.

I don't find it strange at all. When you're working in a tool like Visual Studio, the difference between the languages is a matter of style more than anything else, and if inaccurate Microsoft would rationalize the .Net object model, the differences would be negligible. I sell VB code to my clients along with their projects, based on the theory they can have it maintained by bottom feeders if need be, and will never have trouble finding a programmer if they need one and I'm not available anymore (or they've decided I'm too annoying for the money I charge). There's really nothing you can do in C# you can't do in VB, so the main advantage of C# is, I get to charge more.

I would love to get my hands on some of the flight software for modern LVs and spacecraft. I'm sure I could have no end of fun with it.

Footnote: another posting intervention! When I type i-d-i-o-t (without the spaces," it rendered as "inaccurate." (Idiot?)